Spirorbis spirorbis builds a tiny, left-coiling calcareous tube just 2–3 mm in diameter, white and tightly spiralled like a miniature snail shell. The worm inside extends a fan of tentacles for filter-feeding and broods its larvae internally before releasing them as competent settlers. This species favours the fronds of brown algae (Fucus, Laminaria) in nature but readily colonises nylon netting, polypropylene ropes, and plastic floats on aquaculture installations across the North Atlantic.
A single Spirorbis tube is inconsequential. But settlement densities can reach 200–500 individuals per square decimetre on sheltered net panels, creating a sandpaper-like texture that traps silt and provides footholds for secondary foulers such as hydroids and filamentous algae. The roughened surface also increases hydrodynamic drag beyond what the worms’ mass alone would produce. On long-deployed equipment — mooring ropes, buoy tethers, net pen frames — accumulated Spirorbis coverage accelerates abrasion and shortens service life.
Air-drying kills the worms but leaves the calcareous tubes in place, so mechanical scraping or high-pressure washing is needed for full removal. Anti-fouling coatings based on copper or silicone reduce initial settlement, though Spirorbis larvae are less sensitive to copper than barnacle cyprids. Because this species contributes to the early fouling community that enables heavier organisms to establish, controlling it early pays dividends later. See the methods comparison for coating options, or explore other tubeworm species in the organisms database.
Control Methods
Air-drying Mechanical scraping Anti-fouling coatings